The statement of Amar bin Al-Aas (rta) was correct because the law in presence of a Rasul is different where because of itmam-e-hujjah, every active enemy of Rasul is bound to be destroyed and is bound to go to Hell because in such matters truth is bound to be clear for the addressees of a Rasul. Amar bin Al-Aas (rta) is referring to his emotions of enmity against Prophet Muhammad (sws) which made him blind towards the truth. One cannot be a true seeker of the truth if he lets his emotions make him blind to the truth. Therefore, there is nothing objectionable in this statement.
The verse quoted by Mr. Abdur Rehman Green i.e. Quran 17:15 “We never punish [any nation] unless We send a messenger [so that he is able to conclusively communicate the truth to it before being punished.]” is about punishment on this earth after itmam-e-hujjah when seen in the context.
For view point of Ghamidi Sahab on Non-Muslims and Jannah, please refer to the following thread:
Discussion 89526
The reference to the narration quoted by the respectable scholar above can be found in the following response by Dr. Irfan Shahzad:
Discussion 87028 • Reply 87101
Regarding agnostics or people who were not sure regarding the truth because of a genuine reason, please refer to the following response by Ghamidi Sahab:
Discussion 69477